Coated spray-weld alloy powders



United States Patent This invention relates generally to metallic powders and more particularly to an improved composition of known metallic powder systems of nickle base, iron base, copper base and cobalt base.

Heretofore, it has been known in the art of welding utilizing metallic powders that in the various welding processes such as flame spraying, flame spraying with molten pool generation, deposition with a plasma heat source, etc. these powders display an appreciable variance in the essential characteristics of surface wettability, deposition efliciency, fluidity and weldability on various base metals. These variances are not only different in the various welding processes but they also differ from one general metallic composition to another. It is greatly desirable in the different welding methods using powder as a vehicle, to improve the performance of the various alloy powders utilized in welding. It is also desirable to achieve to any extent uniformity of the performance characteristics of the various alloy powder systems in different welding processes.

It is the general object of the present invention to avoid the foregoing outlined prior art practices by the provision of an improved metallic powder system capable of highly eflicient deposition by welding.

Another object of the present invention is to improve the ability of a variety of metal powders to be utilized in welding in general and in various powder utilizing welding processes.

Still another object of the present invention is to increase the fluidity of the molten pool generated by welding processes utilizing powder as a welding consumable.

Yet another object of this invention is to provide these improved characteristics to a very broad spectrum of metal powder alloys utilized in welding.

Metal powder alloys utilized as consumables in welding fall within the following categories:

Nickel base alloys Element: Percent by weight Boron .75 to 5 Silicon 1.5 to 6 Chromium (l to Carbon Trace to 1.2 Iron Trace to 6 Nickel (essentially) Balance Iron base alloys Element:

Molybdenum 0 -to 5 Tungsten O to 5 Chromium 0 to Carbon 1 to 4.5 Nickel 0 to 50 Silicon 0 to 5 Boron 0 to 4 Iron (essentially) Balance 3,428,442 Patented Feb. 18, 1969 Cobalt base alloys Element:

Nickel Trace to 40 Chromium 15 to 35 Tungsten 3 to 20 Carbon .05 to 3 Boron 0 to 3.5 Cobalt (essentially) Balance Copper base alloys Element:

Silicon 0 to 3 Manganese 0 to 1 Phosphorus 0 to 9 Chromium 0 to l Tin 0 to 10 Nickel 0 to 30 Copper Balance It has been found that by providing a layer of copper on the outer surface of the metal powders of the above outlined alloy compositions when the powders are utilized in welding processes such as flame spraying, plasma welding, flame spraying with molten pool generation, improved properties are apparent. The copper layer coating ranges from .0625 to 10 per cent copper by" weight and is uniformly distributed on the surface of powders that have a mesh size finer than 30 mesh with the powder mixture containing not more than 15 per cent powders that are capable of passing through a 10 micron sieve opening. It has been found that unexpectedly when these powders are deposited by welding the deposition efiiciencies achieved are tremendously increased over those efliciencies obtained when using the same alloy powders without the copper layer.

After some further experimentation and testing it was found that powders of the alloy system compositions outlined above with the copper layer on the outer surface of the powder, when passing through the flame of a powder spray flame welding unit such as that shown in US. Patent No. 3,226,028, or when passing through the heat source of a welding process readily absorb the heat input which causes the highly conductive discrete copper surface layer to melt. The melting of the copper conveniently located on the surface of these powders thus provides a molten contact adhesive layer which adheres on contact upon spraying to the base metal or the molten pool of a weld deposit minimizing bounce-back of the powders that is prevalent in all of the described metal powder systems but is especially a problem in the highly melting alloy powders such as the cobalt or iron base alloy powders. This is found to be true even in the powders that are passed in the outer extremities of the heat source or flame. Thus the deposition efliciency of the copper coated layer powders has been substantially increased even in the higher melting alloy powders. These same higher melting alloy powders without the copper layers are normally deposited with lower deposit efiiciencies because of the higher heat required by these alloy powders to produce a molten or platsic pool on their surface. When these alloy powders as well as other alloy metal powders are deposited on base metal through a pressurized source, they bounce off the base metal and do not enter the molten pool.

Additionally, these copper coated metallic alloy powders show surprisingly improved fluidity and Wetting of the surface of the base metal which is attributed to the alloying of the copper that occurs in the molten pool through the welding process. Coincidentally, the copper content in some of these alloy systems results in improvement, in some cases, in the weld deposit having increased resistance to corrosion.

Additional fluidity and surface wettability of the deposited alloy can be obtained by providing on the copper layer surface or alloyed with the copper, an additional layer of phosphorus with the phosphorus ranging from .004 percent to .035 percent by weight. Here the phosphorus on the surface combines its characteristics with the characteristics of the copper alloy outlined above, considerably lowering the melting point and enhancing the fluidity and surface wettability of these alloys, further promoting the ability of these alloys to display good as well as uniform weld deposition characteristics.

The provision of the copper layers on the metallic alloy powders can be accomplished by any of the well known copper plating processes such as for example immersing the alloy powders in a copper sulfate solution bath and, likewise, the phosphorus layer on the copper can be achieved by treating the copper layer containing powders in a hydrogen phosphate bath or in a dry mixture with copper phosphate with the plating generated by either chemical or electrical means whereby electrolysis or deposition is accomplished.

Additionally, there has been a need for obtaining uniform basic coloring and coloring techniques in metallic powder systems. Color codes have found utility in industry for easily distinguishing products with particular characteristics. The copper layer and the phosphorus layers on the metallic powders have also been found to produce distinguishable coloring to the powders, which coloring can be controlled for the alloy systems outlined herein in predetermined shading ranging in the yellow-red-orange spectrum dependent upon the thickness of the copper, and phosphorus content as per the percentages described herein.

Additional colors on the metallic powder alloy systems outlined above can be achieved by diffusion and slight oxidation of the copper phosphorus layers and/or copper phosphorus alloy on the metallic powders. The slight oxidation of the copper phosphate layers produce colorings in the gold-purple-blue-green spectrum depending on the amount of oxidation to be tolerated. It has been found that ranges of .003 percent to 1 percent by Weight of generated oxide of copper achieve best tolerated results on the copper layer containing metallic powders, and ranges of .008 percent to .027 percent by weight of generated oxide of phosphorus achieve best tolerated results on the phosphorus top layer containing metallic powders. Achievement of the generated oxides of copper and phosphorus and/or the alloys thereof can be achieved by a number of methods such as by chemical or electrical displacement by immersing the powders in various chemicals and/or controlled oxidation in the atmosphere.

Additionally, still further coloring of the metallic alloy powders can be achieved in the gold-grey-aqua spectrum by further alloying with the copper coatings of .04 to 3 percent by weight of gold; .04 to 6 percent by weight of silver and .03 to percent by weight of platinum. The coating layers can be achieved by chemical electrolysis or chemical displacement as for example, placing the copper coated powder in a salt solution of the aforementioned element.

It will now be understood by those skilled in the art that the objects of this invention have been achieved by providing improved alloy powders for welding which provide improved welding efficiency, better surface wettability and beter fluidity of the weld deposit. In addition a system has been provided for coloring the metallic alloy powders.

Although in accordance with the patent statutes a preferred embodiment of the invention has been outlined in detail, the scope and spirit of this invention is not to be limited thereto or therebv.

position taken from QJJQMQLJhe groups of the following alloy systems:

Element: Percent by weight Boron .75 to 5 Silicon 1:5 to 6 Chromium 0 to 20 Carbon Trace to 1.2 Iron Trace to 6 Nickel (essentially) Balance Element:

Molybdenum 0 to 5 Tungsten 0 to 5 Chromium 0 to 30 Carbon 1 to 4.5 Nickel 0 to 50 Silicon 0 to 5 Boron 0 to 4 Iron (essentially) Balance Element:

Nickel Trace to 40 Chromium 15 to 35 Tungsten 3 to 20 Carbon .05 to 3 Boron 0 to 3.5

Cobalt (essentially) Balance Element:

Silicon 0 to 3 Manganese 0 to 1 Phosphorus 0 to 9 Chromium 0 to 1 Tin 0 to 10 Nickel 0 to 30 Copper Balance and said alloy powders being provided Lillian. outer layer of cqpner.

2? The alloy powder of claim 1 wherein said powders are provided with a surface layer of phosphorus.

3. The alloy powder of claim 1 wherein said copper outer layer comprises .0625 to 10 percent by weight.

4. The alloy powder of claim 2 wherein said phosphorus layer comprises .004 to .035 percent by weight.

5. The powder of claim 3 wherein said powders have a predetermined coloring.

6. The powder of claim 4 wherein said powders have a predetermined coloring.

7. The alloy powder of claim 1 wherein the powder particle size is finer than thirty mesh.

8. The alloy powder of claim 2 wherein the powder particle size is finer than thirty mesh.

References Cited UNITED STATES PATENTS 3,238,060 3/1966 Quaas et al 117--105.2 3,254,970 6/1966 Dittrich et a1. 29-1912 X 3,276,893 10/1966 Quaas et a1 117105.2 X

3,322,547 5/1967 Quaas et al l17105.2 X

L. DEWAYNE RUTLEDGE, Primary Examiner.

E. L. WEISE, Assistant Examiner.

U.S. Cl. X.R. 

1. A METAL ALLOY POWDER COMPRISING POWDER OF A COMPOSITION TAKEN FROM ONE OF THE GROUPS OF THE FOLLOWING ALLOY SYSTEMS: 